This proposal describes projects designed to analyze several different aspects of the structure of genetic material in eukaryotes. 1) We have succeeded in obtaining radiochemically pure mitochondrial messenger RNAs from Drosophila melanogaster. These mRNAs will be used to map the coding sequences on the restriction map of mitochondrial DNA. Further characterization of the mitochondiral mRNA will be attempted by using cell-free transcription and translation to determine the protein product of each gene. 2) The giant lampbrush chromosomes in the oocyte nuclei of salamanders give exceptional resolution for the analysis of DNA sequence organization. In addition they are active in transcription and thus provide a way of visualizing genetic activity during much of the period of oocyte development. In situ hybridization with 3H cDNA will be used to study DNA sequence arrangement in the chromosomes and to identify the RNA sequences associated with the lampbrush loops. 3) Inverted repeat DNA sequences have been found in the nuclear DNA of all eukaryotes studied. We will use me3-psoralen crosslinking and electron microscopy to analyze the in vivo secondary structure of DNA in several cell types to study possible functions of this DNA.